Stepper code from app notes work?

edmondfox

I am attempting to use the code I found in the stamp app notes to run a stepper motor and allow me to change the delays and speed of motors. However when I try to run the program I get errors that say invalid character on the pound signs as in '#Steps'. Is there a special way to compile adn run this code? I have tried on both a stamp1 and stamp 2 controller. THe code is below :

' Program STEP.BAS


' The Stamp accepts simply formatted commands and drives a four-coil stepper. Commands
' are formatted as follows: +500 20<return> means rotate forward 500 steps with 20
' milliseconds between steps. To run the stepper backward, substitute - for +.

Symbol Directn = B0
Symbol Steps = W1
Symbol i = W2
Symbol Delay = B6
Symbol Dir_cmd = B7

DIRS = %01000011 : pins = %00000001 ' Initialize output.
B1 = %00000001 : Directn = "+"

GOTO Prompt ' Display prompt.

' Accept a command string consisting of direction (+/-), a 16-bit number
' of steps, and an 8-bit delay (milliseconds) between steps. If longer
' step delays are required, just command 1 step at a time with long
' delays between commands.

Cmd: SERIN 7,N2400,Dir_cmd,#Steps,#Delay ' Get orders from terminal.
IF Dir_cmd = Directn THEN Stepit ' Same direction? Begin.
B1 = B1^%00000011

' Else reverse (invert b1).

Stepit: FOR i = 1 TO Steps
' Number of steps.
pins = pins^B1
' XOR output with b1, then invert b1
B1 = B1^%00000011
' to calculate the stepping sequence.
PAUSE Delay ' Wait commanded delay between
' steps.
NEXT
Directn = Dir_cmd
' Direction = new direction.

Prompt: SEROUT 6,N2400,(10,13,"step> ") ' Show prompt, send return
GOTO Cmd ' and linefeed to terminal.

Jon Williams

That code is very old but it does in fact compile. Make sure you've selected the BS1 in the editor with these lines at the top of the program:

' {$STAMP BS1}
' {$PBASIC 1.0}

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Jon Williams
Applications Engineer, Parallax

edmondfox

Thanks, I over looked that. One other question, how do I connect to the stamp to get the prompt to enter data?

Jon Williams

That's a very old app note and as I remember you have to use an external termina with a 22K resistor in the serial input line. Is that what you want to do? If you just want to do stepper control, check our stepper docs for updated code (control only -- no serial input).

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Jon Williams
Applications Engineer, Parallax

edmondfox

I need to be able to enter the delay and speed with a console. I want to make a windows frontend to send the data over the serial port.

edmondfox

I have another question concerning this code, in it there are binary strings that represent the stepping sequences of the motors. How do I go about deriving my own for another set of stepper motors? How were those in the app nots derived?

Jon Williams

Step sequences come from motor information.· As far as I know, you'd only have two possible sequences for steppers: full-steps and half-steps.· Our documentation for the stepper motor we sell shows both.

http://www.parallax.com/dl/docs/prod/motors/27964.pdf

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Jon Williams
Applications Engineer, Parallax

Larry

I can think of a third sequence, John.
steppers can do a full step sequence with either 1 or 2 coils energized at all times.

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Jon Williams

I've only every seen sequences with four steps (two coils engergized) or eight steps (one or two energized). Since there's only four coils I'm not sure if doing a four-step sequence with only one coil engerized would be useful (if it would work at all).

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Jon Williams
Applications Engineer, Parallax

Larry

let me refer you here:

http://www.doc.ic.ac.uk/~ih/doc/stepper/control2/sequence.html

you will see that single coil excitation does indeed work.
it runs at lower torque, but at lower power and gives smoother motion of the stepper.

Often used in telescope control

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edmondfox

I have been messing with the above code I posted to run 2 motors, however I am still having trouble with the sequence. It is my understanding that the binary strings somehow reperesent the sequence of the motors. However I have been unable to decipher them after looking at them for a while. Below is the code I have and a link to a pdf with the motors sequence. If it is not too much trouble can you help me with the proper values.

Main:

Cmd:
SEROUT Sio, Baud, [noparse][[/noparse]"Cmd>"]
SERIN Sio, Baud, [noparse][[/noparse]Dircmd1, DEC Steps1]
SERIN Sio, Baud, [noparse][[/noparse]Dircmd2, DEC Steps2]
SERIN Sio, Baud, 2000,nodata,[noparse][[/noparse]DEC SLEP]

noData:

IF Dircmd1 = Directn1 THEN DL1
M1 = M1^%0000000000000011
DL1:

IF Dircmd2 = Directn2 THEN DL2
M2 = M2^%0000000000001100
DL2:

C = Steps1

IF C > Steps2 THEN IFL1
C = Steps2
IFL1:

FOR I = 1 TO C

IF Steps2 = 0 THEN skip2
IF I > Steps2 THEN skip2
OUTS = OUTS^M2
M2 = M2^%0000000000001100
skip2:

IF Steps1 = 0 THEN skip1
IF I > Steps1 THEN skip1
OUTS = OUTS^M1
M1 = M1^%0000000000000011
skip1:

PAUSE SLEP
NEXT
Directn2 = Dircmd2
Directn1 = Dircmd1

GOTO Cmd

END

http://www.thelegionofblood.com/motor.pdf

Jon Williams

I believe you start with an old BS1 app note -- remember the BS1 was "pin shy" and Scott (author of that app note) used a clever trick to minimize IO requirements. Since you're using a BS2 let me suggest that you use direct outputs to the motor coils (through an appropriate driver, of course). The great thing about the BS2 is that its outputs are divided into 4-bit chunks, so that makes stepper connecting very simple -- you just write the 4-bit sequence state to the appropriate output block. Our stepper documentation shows how to do this and it could be easily adapted.

If you can't do that then you'll have to use some separate bits of memory to hold the current state of each motor output, then OR them together and place on the physical pins. That way you can change one motor without affecting the other.· And no, in the original version the binary values are not a direct representation of the coil states.· Again, the code in our stepper motor documentation DOES have a direct relationship in that regard and is far easier to adapt.

http://www.parallax.com/detail.asp?product_id=27964

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Jon Williams
Applications Engineer, Parallax

Jon Williams

The great thing about having a PDB on my desk and a TV in my office, is that I can have fun on a Sunday while watching the Cowboys play.· I've attached a BS2-based program that will control two steppers (using a 4-step sequence) through a terminal.· The input is:

· motor direction steps

So if you want to move motor 1 forward 100 steps you would enter this at the prompt:

· 1+100<CR>

For testing I connected the outputs to PDB LEDs and could see that both were operating as expected.· In the code the RxD and TxD lines are both assigned to pin 16 -- this is so I can manually open a DEBUG window and use it as a terminal.· Give it a try and them modify it as you need.· Note that the program takes advantage of the BASIC Stamp's implicit array structure in RAM and the output registers are part of RAM, so

· Motor1(1) is the same as Motor2

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Jon Williams
Applications Engineer, Parallax

edmondfox

Thanks, that works. However I don't understand how this part works:

Move_Motor:
FOR movement = 1 TO numSteps
-> READ Steps + idx(mNum), Motor1(mNum)
-> idx(mNum) = idx(mNum) + offset // 4 ' update table pointer
PAUSE StepDelay
NEXT

and how I could use it to turn the 2 motors with 2 different number of steps.

Also, can the stamp be used to tokenize a string that is sent to it that contains the parameters? Is it feasible to implement a tokenizer on the stamp, would it take too much time?

I ask because I have written a windows app to collect the data from the user and send it over the serial port to the stamp, however it sends it as an array of characters.

Jon Williams

The way I wrote the program you only send one motor control at a time.· If you want to send both, then you'll have to adjust the software -- I chose one at a time because it would be you would have to send a 0 steps movement for a motor you don't want to adjust.· Once you understand this program, making that adjustment won't be hard.

On READ: That is used to read the motor outputs from a DATA table.· Since you have two motors and the could each be moved a different number of steps, each has its own index pointer ( called idx() ) into that table.· The variable called mNum will resolve to 0 or 1 to select which index is being used.· Likewise that index will be used to point the value read from the table to the correct set of outputs.

This program uses the fact that anything in the PBASIC RAM can be treated like an array.· Notice that I have declared the outputs for the first motor on OUTA (pins 0 - 3), and the second motor on OUTB (pins 4 - 7).· Because of the implicit array structure I can refer to OUTA as Motor1(0) and OUTB as Motor1(1).

The next lin increments the pointer to the next position and uses modulus to wrap around at either end.· Modulus is a great tool that some many people neglect.· In simple terms, // returns the remainder of a division.· So, if you divide by N, // will return a value between 0 and N-1.· When incrementing the table, the step pointer works like this:

· 0 + 1 = 1 // 4 = 1
· 1 +·1 = 2 // 4 = 2
· 2 + 1 = 3 // 4 = 3
· 3 + 1 = 4 // 4 = 0
··0 + 1 =·1 // 4 = 1·· <-- the pointer just wrapped around

Going backwards is similar, but instead of adding one we add the division minus 1.

· 0 + 3 = 3 // 4 = 3
· 3 + 3 = 6 // 4 = 2
· 2 + 3 = 5 // 4 = 1
· 1 + 3 = 4 // 4 = 0
· 0 + 3 = 3 // 4 = 3·· <-- the pointer just wrapped around

I have no idea what you mean about implementing a tokenizer on the Stamp -- You could certainly compress values sent to it and use the Stamp to decode them, but I think this would probably not be worth the effort in most cases.

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Jon Williams
Applications Engineer, Parallax

edmondfox

Thanks so much for helping me with that. I have another question, not related to the stepper motors but to the input of the program. I have written a windows interface to send the data to the stamp over the serial port, however I can only get the data to be sent as an array of characters, not integers like the stamp expects. Do you have any ideas what I can do on the stamp side to take this data and convert it to the proper form so that stamp can use it to run the motors?

Jon Williams

Move new questions to new threads, please.

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Jon Williams
Applications Engineer, Parallax